1. Field of the Invention
This invention relates to an aqueous electrolyzed solution prepared by electrolysis of a starting aqueous solution of ascorbyl glucosamine, which has a lower oxidation-reduction potential than the starting aqueous solution of ascorbyl glucosamine, as well as a preparation process therefor.
2. Description of the Related Art
It is a well-known technique that a dilute starting aqueous solution of an electrolyte (e.g., an alkali-metal chloride) as an electrolysis aid is electrolyzed in an electrolytic cell while removing an aqueous anodic electrolyzed solution with a lower pH generated around the anode (acidic water), which is then utilized for sterilization or disinfection (JP-A 6-246272). The electrolytic cell internally comprises inactive electrodes made of, e.g., platinum or a platinum alloy separated by a septum. The septum used is a charged membrane which is an ion-exchange resin film or a non-charged membrane having a microporous structure.
The aqueous anodic electrolyzed solution formed around the anode contains hypochlorous acid. Potent oxidizing and chlorinating action of hypochlorous acid has been widely utilized for sterilization or disinfection in medical institutions. In addition, since a small amount of ozone and/or dissolved oxygen in the acidic water can promote granulation, the acidic water has been studied for its use as an aid in surgical treatment.
An aqueous cathodic electrolyzed solution formed around the cathode (alkali water) may be also prepared by electrolyzing tap water in place of a dilute aqueous solution of an electrolyte and has been, for example, used for drinking.
It is also known technique that the above aqueous electrolyte solution comprising an organic acid such as ascorbic acid or gallic acid as an additive rather than as an electrolysis aid is electrolyzed (U.S. Pat. No. 5,736,027).
In the above process, ascorbic acid is used in the presence of an electrolysis aid. Ascorbic acid is added for controlling pH of the aqueous cathodic electrolyzed solution and removing free chlorine in the aqueous anodic electrolyzed solution.
Ascorbic acid (also called as vitamin C) is widely contained in fruits, vegetables or other foods. Particularly, antioxidative effect of ascorbic acid has been recently paid attention and thus ascorbic acid has been added to a product such as health foods and cosmetics for endowing these with the effect.
Antioxidative effect of ascorbic acid has been generally recognized since its disproportionation effect on superoxide anion radical which is a kind of radical (conversion of superoxide anion radical into hydrogen peroxide) was reported. Since Friedvich found superoxide dismutase (SOD), an enzyme capable of disproportionating superoxide anion radical, in 1869, antioxidating effect of ascorbic acid has been much more paid attention.
We have already filed a patent application based on an invention related to a process for preparing an aqueous anodic electrolyzed solution using ascorbic acid itself as an electrolysis aid (P 2001-347269A JAPAN).
Since ascorbic acid is extremely susceptible to oxidation, it is believed that keeping its quality stable is difficult. In particular, ascorbic acid in an aqueous solution is oxidized while being spontaneously decomposed. It cannot, therefore, stably exist for a long period. Furthermore, in an aqueous solution containing much dissolved oxygen, ascorbic acid is spontaneously decomposed into an oxidized form of ascorbic acid for a short time and thus lose its antioxidating effect. In preparation of an aqueous electrolyzed solution using ascorbic acid as an electrolysis aid, there is, therefore, a problem that an aqueous ascorbic-acid solution as a starting aqueous electrolysis solution cannot be stably stored for a long time.
We have made various attempts for solving the above problems and thus have hit an idea of using ascorbyl glucosamine as an electrolysis aid. Ascorbyl glucosamine has a complex in which ascorbic acid is surrounded glucosamine, and the structure allows ascorbic acid to have antioxidating effect. As a result, ascorbyl glucosamine can exhibit stable antioxidating effect.
In the fields of medical drugs, cosmetics and foods, decomposition of ascorbic acid in an aqueous solution has been prevented by any of known methods; for example, retardation of spontaneous oxidation of ascorbic acid by adding an antioxidant such as vitamin E and gallic acid. Examples of a stable form of ascorbic acid include ascorbyl palmitate prepared by reaction of a palmitate with ascorbic acid.
Since ascorbyl glucosamine is soluble in water and exhibits higher permeability to a skin, it has been utilized for skin care including cosmetics. In addition, ascorbyl glucosamine can suppress collagenase activity inhibiting collagen formation. Ascorbyl glucosamine has been, therefore, utilized in the field of cosmetics as an extremely effective promoter for forming collagen.
We have not found any report in which ascorbyl glucosamine is used as an electrolysis aid.
Thus, an objective of this invention is to provide a stable aqueous electrolyzed solution of ascorbyl glucosamine and a preparation process therefor.
To achieve the above objective, this invention provides:
[1] an aqueous cathodic electrolyzed solution of ascorbyl glucosamine exhibiting a lower oxidation-reduction potential than that in a starting aqueous solution of ascorbyl glucosamine in which a concentration of water-soluble inorganic salts is less than 0.1 M;
[2] the aqueous cathodic electrolyzed solution as described in [1] wherein a concentration of ascorbyl glucosamine is 0.1 to 3 wt % in the aqueous cathodic electrolyzed solution of ascorbyl glucosamine;
[3] the aqueous cathodic electrolyzed solution as described in [1] wherein the amount of dissolved oxygen is 0.2 to 0.5 mg/l in the aqueous cathodic electrolyzed solution;
[4] the aqueous cathodic electrolyzed solution as described in [1] exhibiting a lower oxidation-reduction potential by 100 mV or more than that in the starting aqueous solution of ascorbyl glucosamine;
[5] a process for preparing an aqueous cathodic electrolyzed solution of ascorbyl glucosamine comprising the step of electrolyzing a starting aqueous solution of ascorbyl glucosamine in which a concentration of water-soluble inorganic salts is less than 0.1 M to removing from the cathode side an aqueous electrolyzed solution of ascorbyl glucosamine exhibiting a lower oxidation-reduction potential than that in the starting aqueous solution of ascorbyl glucosamine;
[6] the process for preparing an aqueous cathodic electrolyzed solution as described in [5] wherein a concentration of ascorbyl glucosamine is 0.1 to 3 wt % in the starting aqueous solution of ascorbyl glucosamine;
[7] the process for preparing an aqueous cathodic electrolyzed solution as described in [5] wherein a current density in electrolysis is 0.003 to 0.03 A/cm2.
According to this invention, the starting aqueous electrolysis solution is stable to oxidation because the starting aqueous solution is prepared using ascorbyl glucosamine, an ascorbic-acid derivative, as an electrolysis aid. An aqueous cathodic electrolyzed solution obtained is also stable to oxidation. The aqueous cathodic electrolyzed solution obtained is also extremely highly reductive. According to this invention, ascorbyl glucosamine having excellent antioxidating effect can be electrolyzed to provide an aqueous cathodic electrolyzed solution containing highly active dissolved hydrogen. The aqueous electrolyzed solution can be applied to a skin to exhibit excellent effects such as prevention or repair of oxidative skin damage.